1. Field of the Invention
The present invention relates to a photographic light-sensitive silver halide material for forming direct-positive images, in particular computer output (COM) images, said material having a reduced tendency of getting sensitized under the influence of mechanical pressure exerted thereon in the period starting with its manufacture up to its development. The invention also relates to a method for making direct-positive images with such a photographic light-sensitive silver halide material.
2. Background of the Invention
In silver halide photography a photographic method, according to which a positive image is made without the use of a negative image or an intermediary process producing a negative image, is called a direct-positive method and a photographic light-sensitive material and a photographic emulsion for use according to such direct-positive method are called direct-positive material and direct-positive emulsion respectively.
Because of their practical and economical usefulness in the field of printing out of computer information preference is given nowadays to the use of direct-positive materials and direct-positive emulsions.
A variety of direct-positive photographic methods and materials are known. The most useful methods are the method, which comprises exposing a photographic material comprising prefogged silver halide grains to light in the presence of a desensitizing agent and developing them, and the method, which comprises subjecting a photographic material comprising silver halide grains that have light-sensitive specks mainly inside the grains to an image-wise exposure and developing the exposed material in the presence of a development nucleator or developing the exposed material after overall light-flashing it to fog. The present invention relates to the latter method and to photographic material comprising silver halide grains that have light-sensitive specks mainly inside the grains . Such a photographic silver halide emulsion material, which forms latent images mainly inside the grains, is referred to as internal latent image-type silver halide emulsion material, and thus is distinguished from silver halide grains that form latent images mainly at the surface of the grains.
It is known to develop a latent image that has been formed mainly inside the grains by means of a so-called internal developer, but the material and the emulsions used in accordance with the present invention are not concerned with that type of development, but rather with the type of development using a so-called surface developer.
It is also generally known that mechanical pressure applied to the photographic silver halide emulsion material in the period starting with its manufacture up to the development can produce both reversible and irreversible effects. Mechanical pressure can cause irreversible distortion of the emulsion grains or the formation of physical defects that alter the sensitivity for latent-image formation. Mechanical pressure can change the sensitivity of the emulsion coating, when it is applied before, during, or after the exposure thereof. A photographic direct-positive silver halide emulsion material comprising silver halide grains that have light-sensitive specks mainly inside the grains is particularly susceptible to sensitization under the influence of mechanical pressure in that at the places where pressure has been exerted unwanted white streaks or markings are left upon development.